Piston



D. BUSHBY Nov. 3; 1942.

rIs'roN Filed Jan. 15. 1940 2 Sheets-Sheet 1 X. mw am.

Nov. 3, 1942.

D. BUSHBY PISTON Filed Jan. l5. 1940 2 Sheets-Sheet 2 ,ture and repair.

Patented Nov. 3, 1942 PISTON David Bushby, Regina, Saskatchewan, Canada,

assignor to The Vacuum Air Pressure Company Limited, Regina, Saskatchewan, Canada Application January 15, 1940, serial-N0. 314,004

` s claims. `(01.'309-411) My invention relates to improvements in pistons and the principal object of my invention is to provide a device of the character herewithin described which particularly when used in as.-

sociation with internal combustion engines and',

the like, maintains for a longer period of operation a considerably higher compression sealing eii'ect than has previously been obtainable in cylinders employing pistons of conventional design.

A further object of myinvention is to provide a device of the character. herewithin described wherein the elongation of the cylinder bore caused by the action of the piston is eliminated by a circumferential equalization of the piston Wear. s

A further object of my invention is to provide a device of the character herewithin described in which the necessity of conventional piston cam-grinding is avoided by a circumferentially uniform coeicient of piston expansion. Y

A further object of my invention is to provide a device of the character herewithin described wherein an automatic means is incorporated for `maintaining. the high compression assembly in proper contact with the cylinder wall, simultaneously preventing the leakage of compressed gases therebetween and the body of the piston. Y

A further object of my invention is to provide a device of the character herewithin described in which the conventional practice of installing new rings into the worn ring grooves of an old piston is eliminated by the provision of a replaceable high compression assembly retaining means.

A further object of my invention is to provide a device of the character herewithin ydescribed, which will outlast the conventional piston in operation, maintain a constant highly eiiicient compression sealing effect to the' end of its life and render itselfjeconomical to manufac- With the above more important objects in view and such other minor objects as may appear as the specification proceeds, my invention consists essentially in the arrangement and construction of parts all as hereinafter more particularly described, reference being had to the accompanying drawings, in which:

Figure l is a vertical cross-sectional elevation of my piston and high compression assembly .showing the same in a new or unworn' condition.

Figure 2 is a sectional elevation.l along the line 2-'2.in Figure l, but showing my compression assembly asbeing partially worn.

Figure 3 is a perspective illustration of one oflmy annular springs incorporated in the subkject matter of Figures 1 and 2.

In the drawings like characters of reference indicate corresponding parts in the different figures.L

'My vpiston I is provided with a lateral wall I of substantially a smaller diameter than the bore f' of. the cylinder Walls 2 to accommodate my'high compression assembly 3 therebetween. The latter is positioned subjacently to an annular flange 4 formed by the piston head I and its various'constituents are retained in position by means of the snap rings 5, 6, 1 land 8, engaging annular recesses 5', 6', 1 and 8 provided in the piston wall I,"the rings 5, 6, 1, and 8 being what I call groove-forming rings inasmuch'as they act as one of the Y annular projecting boundaries of the adjacent groove.

My high compression assembly 3 includesv a pair of split, interlocking compression rings 9 and III. The former has the upper edge 9 thereof in engagement withthe flange 4, and is provided with a circumferential recess II designed -to receive a split compression seal ring I2.

The adjacent edges of the rings 9 and I0 are vcomplementarily rabbeted as at I3 to facilitate linterlocking and the ring I0 has its lower edge recessively'chamfered to provide an undercut irecess I4, a cuneiform cross-sectional configura- 'I' and the flange 4 respectively onthe diametrically opposed sides of the piston I and engage the slots of the split rings 9 and I0 as best illus- -trated in the accompanying Figure 2. y

The aforementioned snap-ring Sretains the interlockedA ring assembly 9, I0 and I2 thus formed in position against the piston ange 4,

vyet permits any diametrical expansion thereof as may be imparted to it by 'a spring pressed sliding sleeve 20 detailed hereinafter.

An intermediate annular skirt I1 is freely mounted upon the piston wall I essentially medially of the length thereof'and in spaced'relationship in respect to the lower compression ring I0. A pair of the aforementioned snap rings 6 and 1 engage the upper and lower edges of the. skirt I1 respectively and the latter is split 1n a slmilar manner to the compression rings 9,

.I0 andIZ.

a complementary engagement with the aforementioned cuneiform recesses I4 and I8 respec` tively and spaced apart by a spring means 23.

The spring means 23 may 'assume thejforrn` clearly illustrated in Figure 31 ofthe accompanying drawings and comprises a split annular s'teel of dimensions for manufacturing purposes which 'in view of this disclosure I consider to entail merely mechanical skill together with the skill of the mechanical draftsman, and since many apparently widely different embodiments of this spring 24 alternatively depressed and 'elevated-fas at 25 and 25 respectively, to produce -a .ring

member of the desired width and resiliency.

The spring 23 engages a pair, of annular grooves 25 and126' formed medially in the opposing extremities or edges of the sleeves 20, 2B' respectively, and a freely mounted spacing ring 21 is loosely interposed therebetween toprevent an actual contact thereof.

The inner surfaces of the 'sleeves 20, 20'. are stepped back as at 28 so that the intermediate surfaces 2I partially overlap the snap: rings 5 and 6, and in thisconnection it will be seen that a space 28 exists between the riser 29 and the opposing edges of the snap rings 5 and 6 when the assembly is'unworn as perrtheaccoinpanying Figure 1.

Positionedimmediately Ibelowthe skirt I'I I provide an annular sleeve .and .spring arrangement to the 'aforementioned' sleevesi 20, 20.',` the spring 23 and the spacing ring 2'I,`namely..an additional annular spring pressed slidingY sleeve 29', a spring means `30 and a spacing ringA 3l, all above parts being identical in structureto those already'idetailed and hence requiring v.no further explanation.

The spring 30 at thelower points of contact thereof engages anv annular' groove .32 similar to the previously `mentioned grooves 26` and `2li' formed in the upper 'edge of an annular `retaining ring 32'.

The latter is retained near the lower extremity ofthe piston wall I by means of the snap-ring 8 and is provided with an annular circumferential groove 33 designed to yreceive a split oil ring 34.

When my piston and high compression assemb-ly A is placed in'operation, it will lbe 'observedthat the slidingsleeves S20, 2Iland 29 under the actuation of the spring means 23 and 3D will constantly urge the 4interlocking compression ring assembly Q, ID and 'I2 outwardly against the cylinder walls 2 under-progressive `conditions of wear.

ject to a balanced coefficient of expansion under kthe presence of heat.

Finally,- when after a considerableperiod .of 'usage it becomes necessary to replacelmyf high invention may be made within the scope of the accompanying claims Without departing from the spirit and scope of the same, it is intended that all matter contained in the accompanying speci- -cati'on shall be interpreted as illustrative only and not in va limiting sense and I desire only suchlimitations placed thereon as justice dictates.

. What I claim as my .invention is:

1. A .piston and high vcompression assembly positioned thereon embodying .a .compression ringlhaving one edge'thereof recessively chamfered andan annular spring pressedsleeve having one edge thereof bearing against said lrecessively chamfered edge and movable in a plane parallel with thepiston axis toforce said ring outwardly .against the surrounding cylinder wall.

2. A piston and high compression assembly position thereon embodyinga lcompression ring having one edge thereof recessively chamfered, an annular freely mounted .skirt upon said piston. andspaced from said compression ring the edge of said 4skirt which opposes the chamfered edge of said ring being chamferedsimilarly to said ring, and a pair of freely mounted annular sleeves surrounding said piston and positioned between said compression ring and said skirt, -said sleeves being spaced apart: by spring means `andoppositely acting under the inuence thereof such that the edge of one of said sleeves engages the chamfered edge of said ring while the other `engages the chamfered edge of said skirt.

3. A piston and high compression assembly positioned thereon embodying a compression ring recessively chamfered upon one edge thereof to provide an undercut cuneiform recess, and an annular spring pressed slidable sleeve having one edge thereof stepped outwardlyvfrom the inner surface of said sleeve to provide an annular projecting ange in engagement with said chamfered edge.

Y l. The piston and ring assembly according to claim 1 which includes a retaining ring provided with an annular groove and an oil ring in said groove.

`5."`Apiston`and high compression assembly positionedV thereon embodying ai pair of interlocking compressionrings having adjacent and complementarily rabbeted edges, Vthe remaining edgefof one of ksaid rings being'recessively chamfered, and an annular spring pressed slidable -sleeve having'one edge thereof bearable against said recessively chamfered edge and movable in a plane parallel with thepiston axis to 'force said ring outwardly-against a surrounding vcylfinder lwall.

S6. IA pistonandhighv compression Vassembly skirt held in place by rings positioned in grooves formed in the wall of said piston, a split compression ring surrounding said piston and spaced from said skirt, said compression ring being recessively chamfered upon one edge thereof to provide an undercut ouneiform recess, said skirt being similarly chamfered upon both edges thereof, a retaining ring upon said piston and spaced from said skirt upon the opposite side thereof to that upon which said compression ring is positioned, a pair of freely mounted annular sleeves surrounding said piston and positioned between said compression ring and said skirt, said sleeves being spaced apart by spring means and oppositely acting under the influence thereof such that one of said sleeves engages said opposing recessively chamfered edges upon said compression ring and said skirt, and an additional annular spring pressed slidable sleeve between said retaining ring and said skirt having one edge thereof in engagement with the remaining recessively chamfered edge of said skirt, all for the purpose of urging said compression ring and said skirt outwardly against the associated cylinder Wall under progressive conditions of wear.

'7. A piston centering ring assembly, comprising in combination, a compression ring recessively chamfered at the rear of the external annular surface thereof, and a source of pressure acting against said charnfer parallel to the axis of said piston and uniformly around the circumference of said ring to force said ring outwardly against a surrounding cylinder wall.

8. In combination with the device as dened in claim 7 a groove-forming ring receivable into a shallow annular groove in said piston, said groove-forming ring projecting beyond the adjacent external piston surface to form one removable wall of the groove for said compression 20 ring'.

DAVID BUSHBY. 

